1. Field of Disclosure
Embodiments of the disclosure relate generally to busbars used in equipment racks, and more specifically, to methods of partially insulating high current busbars.
2. Discussion of Related Art
Centralized data centers for computer, communications and other electronic equipment have been in use for a number of years. More recently, with the increasing use of the Internet, large scale data centers that provide hosting services for Internet Service Providers (ISPs), Application Service Providers (ASPs) and Internet content providers have become increasingly popular. It is often desirable to operate equipment within data centers seven days a week, 24 hours per day, with little or no disruption in service. To prevent any disruption in service, it is common practice in data centers to use uninterruptible power supplies (UPSs) to ensure that the equipment within the data centers receives continuous power throughout any black out or brown out periods. Typically, data centers are equipped with a relatively large UPS at the main power distribution panel for the facility. Often, the UPS is selected to have sufficient capacity to meet the power requirements for all of the equipment within the facility.
In certain circumstances, the UPS may require large conductors or busbars, which can carry large currents and high voltages. In some situations, the busbars need to be insulated to avoid short circuits, and in some situations, the busbars need a coating on the contact surfaces due to Underwriters Laboratories (UL) regulations. Presently, there are several methods to insulate busbars. One such method is to apply an epoxy coating to the busbar so that the busbar can withstand high voltages. The coating applied to the surfaces of the busbar is resistant to oxidation over time, and thereby impedes conductivity, which can lead to a thermal runaway. However, epoxy coatings can be expensive. There are many other coatings to insulate the busbar. One such method is to paint the busbar with an anti oxidizing paste before assembly. Another method is to metalize the surface of the busbar with a metal to provide a low contact resistance and avoid excessive oxidation. Silver, tin, and chrome are common metals for surface coating. Typically, the busbar is coated on the full surface. However, coating the busbar with silver, tin or chrome (such as Chrome III) can be expensive as well. Moreover, these processes may not be recognized by UL. Other methods may include sleeves and large air gaps.
Busbars have historically been made from copper, and copper is still a desirable material for busbars. However, due to rising costs of raw material, aluminum has become more common. Unlike copper, which can be used uncoated up to relatively large sizes, aluminum typically requires some form of surface coating on the contact areas due to the quick oxidation of the aluminum surfaces when exposed to air. Coating busbars with epoxy or similar for insulation purposes is a very effective way of adding security and functionality to the busbar, and the technique is state of the art also for medium voltage.
Aluminum has been used as conductors for decades. Also, a process exist today where parts of an aluminum surface are coated with a metal plating for conducting and other parts are anodized (non-conducting). One process employs the use of Chrome III, which is used to metalize the surfaces of the busbar. A special tape may be applied where conducting is intended. Where no tape is applied, insulation is made by removing the Chrome III in a strong acid followed by an anodizing process. Chrome III is not recognized by Underwriters Laboratories as is tin and silver and nickel.